The present invention relates to a process of extracting hydrocarbons from a diatomite formation. More specifically, the present invention relates to the in-situ recovery of hydrocarbons from a diatomite hydrocarbon-rich formation.
Diatomite-hydrocarbon formations and similar materials are different from the vast majority of grainy or tar sand-like formations. Diatomite formations are composed of hollow siliceous skeletons of single-celled animals referred to as "diatoms." A diatomite-like material is defined as a material which has a surface area and structure which is substantially similar to diatomaceous earth such as porcellanite and the like. In ocean sediments, hydrocarbon-rich diatomaceous earth is sometimes referred to as "diatom ooze" which is normally found at a depth of about 500 fathoms and comprises the empty shells of diatoms. The porous structure and extremely high surface area of diatomaceous earth makes extraction and recovery of the hydrocarbons difficult. Hydrocarbon rich diatomite is sometimes classified as a tar sand, i.e., a sand cemented by a bitumen too viscous to be recovered by conventional crude oil production methods.
The properties of the material preclude the application of most surface hydrocarbon solvent or hot waterflood techniques in-situ. Solvents which displace the hydrocarbons tend to be trapped in the diatomaceous earth structure, thus rendering recovery uneconomical. Steam or aqueous hot-wash floods have difficulty reaching the surface of the diatoms in the formation to remove the hydrocarbons therefrom. Also, steam and water drives tend to have poor injectivity. In addition, the water drives may swell the formation and substantially reduce its permeability or plug the formation. Alternatively, surface processing methods require strip mining. The strip mining is often environmentally unacceptable. The surface methods also have disposal problems with the spent material.
Thus, it would be highly desirable to have a process which can extract in-situ the hydrocarbons from the diatomaceous formation without entraining diatoms in the extracted hydrocarbons and swelling or plugging the formation. It would also be desirable to have a flood material which can easily be separated from the produced hydrocarbons for re-injection.